This is the fourth of the five Elemental Planes, reached by a magic portal from the Plane of Fire.
The Plane of Water is ineligible to leave bones files. The entire level is no-teleport and has an undiggable floor.
The level is almost wholly water, with several moving air bubbles. You arrive on the level in a bubble on the left-hand side of the level; the magic portal to the Astral Plane is randomly placed in a bubble on the right of the level, and drifts with that bubble.
Randomly located around the level are nineteen water elementals, eight electric eels, eight giant eels, nine kraken, four sharks, four piranhas, four jellyfish, and four other random monsters.